Method of preparing an isomerization catalyst for normal paraffins



Patented Oct. 12, 1948 vMETHOD OF PREPARING ,AN ISOMERIZA- TIQN CATALYSTFOR .NOLRMALI'ARAF- FINS RobertwEflBurk, ClevelandJ-Ieights, Ohio,assignor .to'lhe Standard Oil Company,0leveland, Ohio,

a corporation .of Ohio 'No' Drawing. Application Qctoher 28, :1943,Y-SeriaI No. 508,070

3' Claims.

This inventionrelatesto :a new-catalyst for efiectingreactions:involving "aliphatic hydrocar- 'bons,'and to'processes of"treating hydrocarbons in which the catalyst is. used.

, "I "have proposed previously to carry out reactions :of aliphatichydrocarbons using a'catalyst in which .the primary ingredients "arehydrogen fluoride promoted by boron :trifiuorida'and 'de- .-sirableresults have been 'obtained using this "catalyst in a wide variety ofprocesses.

I have discoveredithat' when a number of these processes involvingaliphatic hydrocarbons are carried out using hydrogen fluoride "andboron trifiuoride' in the presence .of an olefin, a new catalys't. isformedin which the olefin-is aninfluence or a component, 'and thatsuperior results-are obtained in many reactions with'thisnew catalyst.The olefin possibly may befregarded as functioning in .the .manner ofa'promoter.

'It'is an object of this invention to provide a new catalyst suitablefor effecting reactions involving aliphatic hydrocarbons.

It is a. 'further object'of the invention 'to'react.aliphatic'hydrocarbons in processes such as isomerizing, averaging,cracking, 'and similar processes of converting aliphatic hydrocarbonsinto others of lower or higher molecular weightor of difierent molecularstructure, usirig'the'newcatalyst to effect these-reactions.

Another obj ectpf the invention-is'the'provision of a catalyst which maybe readil-y*modified in activity so'that-the reaction may be readilycontrolled l by meansof variations in the catalyst.

Anotherobject of the invention is the .provision of a -'catalyst 'fromwhich the ffiuoride constituents are readily separated' from:theolefinicconstituent, and :are available for .the :iormation of an additionalquantity of :the -tcatalyst *from azfresh 'amount'of :ole'finszor for:other purposes.

Another object of the I invention:- is :torprovide :-a catalyst,iwhich:although zcontainingvan 1 olefinic hydrocarbon 'asaningredient,iis' nevertheless:im-

':'miscible with the aliphatic :hydrocarbons being treated inaccordance-with the;process, so :that the catalyst :phase and-thetreated hydrocarbon A can .be readilyseparatedtafter the'treatingsioperaition.

The catalyst of dzhetinventionacompriseshydro gen fluoride, borontrifiuoridaand-en olefin; Fit :existsdnithe liquidiphase. :Hydrogenfluoride boils catrzaboutrGl andcis I thereforea iliquid at temperaturesbelow: about room temperature. :It may r'beikept initheliquidphaseat.highen temperatures by moderate v; pressures. The temperatures .andpressuresusedin'the: above=mentioned hydrocarbon treating; processes areconveniently thosetthat :maintain the :hydrogen rfluoride liquid. Boron:temperatures :and pressures :usually employed. inrthese:hydrocarbonitreating processes. However,

. "2 boron trifiuoridedissolves in liquid hydrogen fluo- "rideto 'agiven extent and'the' amount whichdissolves :at "any given temperaturedepends =0n the "partial pressure of "boron trifluoride. At higher 5partialpressures, largeramounts o'fboron trifiuoride are dissolved.

I'heboron trifluoride dissolved in the hydrogen fluoride in the liquidphase possibly may react at-lea'st 'to some-extent. While anunderstanding -of'the chemistryinvolvedis notnecessary for the practiceof my invention, the iollowing theory-and reactions maybe of assistancein-understanding 'the'results-obtained. *Such'a-reactiomif it occurs,

may be viewed as follows:

:HF+BE3 =?HBF4 (1) Thus the amount of -I-IBF4- formed, if the :reac-'tionsuggested is oorrect,'-is a iunction of the partial pressure of the'boron trifluoride. 'The amount-of *boron trifluoride dissolved in thehy- "drogen fluoride, at any given temperature, may be 'expressed'conveniently'in terms of the-partial pressure of boron trifluor-ide.accordance with the invention, from a trace to 1000 pounds per squareinch, whenpreparing the new catalyst. Generally,:about 25 to 300 poundsThis may varyjin per square inch will be used. However, the

amount 'shoul'd under no circumstances exceed '50 mol per centofthefiuori'des. With partial "pressures usually used the amount doesnot I exwhere R..is.'the olefinresidue'or hydrogen. The

0 entire reaction therefore. may beviewed .as 'fol- The amount .of the,olefin may varyffromextremely/small amounts to .l'00 or more mol per.centleasedon the amount of .boron trifluoride dissolved .in,the'hydrogen fluoride. If the mol ratioeis;less.than.lllll%,Lthecatalystmay be viewed as a mixture of hydrogen fluoride and borontrifluoride (or HP and I-IBF'4) plus the new catalyst. The amount of thecatalyst used in a hydrocarbon treating process may be varied somewhat,and the variation may be accomplished by controlling the amount ofolefin. Amounts of olefin in excess of equal mol proportions with thedissolved boron trifluoride are not disadvantageous except that this mayresult in a polymerization which yields polymers of olefin in the newcatalyst; these may not be as active as the lower olefinic compounds ofthe fluorides. The amount of the olefin is not viewed as critical andany amount of significance reflects an improvement in the process. In acommercial embodiment, however, the amount to be used is that whichresults in optimum yields. Expressed in practical terms the amount ofolefin may be /2 to 25 weight per cent based on the hydrocarbon beingtreated.

The amount of composition of the catalyst and therefore the activity mayalso be controlled by olefin is present in an ample amount and thepartial pressure of boron trifluoride is increased, this will result ina shift of the reaction to the right in Equation 3. On the other hand,if during the reaction the partial pressure of boron trifluoride islowered, this will result in a shift of the reaction to the left.

The ingredients of the catalyst may be brought together in any order orsimultaneously. Generally, it is convenient to feed the fluoridestogether or separately to the olefin, which may be in admixture with thehydrocarbon to be treated.

Alternatively, the olefin may dissolve in one or more of the fluoridesbefore they are contacted with the hydrocarbon. The catalyst so formedis used in treating the hydrocarbon and after the treating process thecatalyst may be separated and re-used for treating a separate amount ofthe hydrocarbon; this may or may not contain an olefin to form anadditional amount of catalyst.

In the application of the catalyst to hydrocarbon treating processes,the olefin may have the same number of carbon atoms as the hydrocarbonto be treated or not. It may be ethylene, propylene, butylenes,amylenes, or other higher olefins; diolefins may also be used if theconditions are controlled to prevent undue polymerization. For example,if n-butane is to be isomerized the olefin may be butene, and if thebutene is initially contained in a mixture with the butane it need notbe separated, at least for the initial fraction to be isomerized. Theolefin need not be in the pure state and may be in the form of crackingcoil stocks or other stocks that are highly olefinic in character.

In averaging, a low molecular weight hydrocarbon such as butane orpentane and a higher molecular weight hydrocarbon, such as those inkerosene, naphtha or gas oil, are reacted with the catalyst to formhydrocarbons of molecular Ill) weight intermediate of the molecularweights of the two reacting materials. In the averaging process theolefin may be contained in either of the hydrocarbon fractions or may beintroduced separately or absorbed in the fluorides in a controlledam-ount. It may be of any molecular weight but preferably the number ofcarbon atoms is not greater than the number of carbon atoms in thehigher molecular weight fraction to be averaged.

In cracking processes using the new catalyst, naphtha, kerosene, gas oilor other stock to be cracked is treated with the catalyst. The catalystmay be formed in situby the presence of olefins in the charge stock,added in controlled amount.

The hydrogen fluoride and boron trifluoride used may be the commerciallyavailable grades. It is not necessary to have chemically pure fluorides.The impurities in the commercial grades including water, which aregenerally present in an amount of not over about one per cent, do notinterfere with the operation of the catalyst. In view of the economicadvantage of using the commercial grade, it is preferred, and

; was used in the following examples.

The conditions under which the catalyst is used will vary somewhat withthe hydrocarbon treating process to which it is applied. It will alsodepend upon the starting materials and the products wanted. Thetemperature in general may vary from 30 to 250 F. Generally a range from0 F. through room temperature to 185 F. is preferred. It is an advantageof the new catalyst that extreme temperatures in either direction arenot needed.

The total pressure may vary from atmospheric to 1000 pounds per squareinch and it must, of course, be equal to or exceed the partial pressureof boron trifluoride. Generally, at least a small total pressure isnecessary which is attributed primarily to the partial pressure of borontrifluoride. The total or gauge pressure is always sufficient to keepthe catalyst liquid at the temperature employed. It is also preferredthat the pressure be sufficient to keep the hydrocarbons liquid at thetemperature employed although this is not essential if thorough mixingof the catalyst and hydrocarbons is secured. At the temperature rangesusually used, it is an advantage that high pressures are not required.

The amount of the liquid catalyst phase used in the process may varydepending upon the reaction and the other conditions and may be from5-300 volume per cent based on the liquid hydrocarbons to be treated. Byliquid catalyst phase I mean the hydrogen fluoride containing the newcatalyst, and/or boron trifluoride since generally there may be hydrogenfluoride in excess of that required for a combination in accordance withEquation 2. It may be that the new catalyst should be regarded as apromoter, but I do not intend that matters of terminology shall alterthe concept here described.

The time of contact between the hydrocarbon and the catalyst may varywith the temperature, thoroughness of contact with the catalyst andother factors, and depending upon such factors, the time may be selectedto give optimum yields. This will be from a few minutes to severalhours. In the examples given later one-half hour is used. However withmore thorough mixing this time probably can be reduced materially.Commercial considerations indicate the time necessary should be theminimum to permit the reaction to go to amsigoie thedesiredfextentundertheother operating 'con ditions.

Iii-general; milder Conditions may-=be used forisomerizingssince"desirable equilibrium conditions are ingeneral'obtained at lower temperatures. (Tracking requires somewhat moredrastic conditions; andhigher: temperature and larger amounts ofcatalyst may be used. Averaging requires a powerful catalyst but thetemperature must be helddown. The various factorsare interdependent. Forexample, if a-lowen-temperature is useda somewhat larger amountofcatalyst may be present to obtain the same-result as would be obtainedwith a higher temperature and a lesser amount of catalyst. While therange of temperature, time of contact, etc. may be the same for allprocesses; this does not mean that the same conditions can be used toeffect difierentprocesses. For'example, ,at a given high temperature,mild conditions may be obtained by low partial pressure of borontrifiuoride, suitable for isomerizing. Thus for almost any temperature agiven mild condition can be obtained by adjusting the other variables,particularly the boron trifluoride partial pressure. It is an importantdiscovery thatin addition to varying'temperature; time of contact,pressurawhich are. variables'the prior art has had available, my:invention. provides a new: variable which can 2 be; readily" controlled;Thus, it is possible to go-from: mild; through intermediate to drasticconditions. merely. by increasing the partial pressure ofboron.trifluoride and inisome' cases also t'he amount'iof olefin; andconsequently an:increase= in the; amount of? the catalyst.- This'mayberof great importance when i using equipment that does not. lend!itself: to changes in temperature; .rateiof flow, etc.

The processes of using? the new catalyst are adapted? either forbatch:operation or. for: con-.- tinuous operation. In the case ofbatch-operati'oir the hydrocarbonstozbe treated; the-fluorides and'theolefinare broughtatogether.in-order into asuitable container or:autoclave, .wheresthey are preferably subjected to agitation, and aremaintained under'temperaturei' and pressureconditions" for: the desiredlengthv of time: Following the treatmentirthe: materials willstratifywhen permittedto come't'ota quiescent state'or, if desired, forces.greater than gravity, such as centrifuging, may be: used to eliect theseparation. Thelighter or upper layer will contain the hydrocarbonswhichhave'been altered in accordance with the process under consideration andthe lower layer will comprise the catalyst phase. If the pressure isreleased orlowered: more or" less of the-new catalyst will bedecomposed, and alarge proportion-of the boron trifluoride'will bereleased as a gas. If the temperature is higher than 67 F. hydrogenfluoride alsowill be'released. However; the separation can-be madeunderpressure andthe catalyst .andthe lower or. heavier layer may bere-used for further treatment' 'ofja further quantity of thehydrocarbon.

In a continuous process the fluorides, olefin; and hydrocarbonorhydrocarbons tobe= treated are fed intoa continuous type mixer, forexample-,1

a. B-stage mixer maintained at the desired tem-r perature' and under theappropriate. pressure. The rate of flow through the mixer'is'adjusted sothat the hydrocarbons are in contact with the catalyst'for the desiredlengthof time. The mixture may be -fed into aseparator where it ispermitted to stratify. The-upper layer containing the hydrocarbonsformed in the'process may be continuously withdrawn and the lower layer-'com= prising 'the catalystaphasemw fbeirecirculated'ito v themixing:zone. If? the olefin is introducedliby way off aseparate" supply it'needrbe' addedionly at'the start of the process andlthefluo'rid'eseolefin 5 catalyst'may be circulated andre-used with'fresh supplies ofthe'hydrocarbons to'be' treated. On the other h and, iftheolefin is-admittedwithxthe hydro-carbon te be treated so :that theamountb'f catalyst gradually builds up or iftheicatalysti-becomes-deactivated through polymerization or. com tinueduse it-may beadesirable to withdrawea; portion or all" of thecatalystphase and'lsubject ittoa relatively highxtemperature, forexample 25ii -600 F." At this temperature thecatalyst-dee composes and"substantially all of the fluorides are liberated" therefrom as gases;These :can be collected and "condensed and/or compressed; and returned'td the mixing zone or stored or other-"- wise -used.

Alternatively, instead of distilling the fluorides; the lewer layer or:catalystphasemayrbe treated withza= material which exerts a solventaction on the' fiuorides: and which' is immiscible with. thehydrocarbons-in the lower layer; or whichforms' a chemical compoundor'com'plex with thefluorides; and frorn which' the fluorides may-be:released later; for example, by heating. Such' a material may-bedihydroxy'fluoboric acid; Another alternative is t'odis'till off a:par-tor: most oftl'ie fluorides-from the lower layer'and remove the restby extractionwithsucli a' material. The hydrocarbons in the upper layeralso can be treated with such amaterial to' extract' fluoridestherefrom.

In either-of the above" processes and especially the continuous process,it? will be seen that fora given temperature; pressure and-time ofcontact; the rate of-the reaction can beadjusted by vary:- ing theamount'of catalyst; This'in efiect can be varied by adjustingthe'partial pressure of the boron trifluoride since, asexplained above,the amount of the fluoride-olefin catalyst maybe viewed as a functionof-f the partial pressure of theboron trifluoride. To lower the pressureit is necessary only to open a valve in the mixer and boron trifiuoridewill be released and can be sent to storage. To increase the pressure,

boron trifluoride from a high pressure storage supply can :be 'a'dmittedto the mixing stage;

The new catalyst, as has been stated'heretofore, is particularly usefulfor effecting reactions with aliphatic hydrocarbons, such as paraffinsandicycloparafiinsz. The" catalystis poisoned: in the presence of'certainfaromatics. To understand the' phen'omena; it seems possiblethat the 'catae lyst and an aromatic'reactg.possibly=in accordl ancewith the following equatiom 7-5 aromatizedi Flielatter'may beaccomplished by solvent extraction in accordance with processes wellknown in the art, or with liquid hydrogen fluoride containing dissolvedboron trifluoride in accordance with my application, Serial Number423,303, filed December 17, 1941, now Patent No. 2,343,744. Thedearomatized stock may then be treated with my new catalyst comprised ofhydrogen fluoride, boron trifluoride and an olefin.

If the stock contains both aromatics and olefins, it may be treated withliquid hydrogen fluoride containing dissolved boron trifluoride andaromatics and olefins will both be eliminated probably throughalkylation of aromatics as described in Equation 4 and the formation ofa complex with the alkylated aromatics which separates in the lowerlayer. If the olefins are present in an excess, the upper layer may thenbe treated to form the new catalyst, or if not a controlled amount ofolefin may be introduced to form the new catalyst.

From the above explanation it will be seen that instances where theolefin for the formation of the new catalyst is to be obtained from anolefinic content in the stock to be treated, the stock should berelatively free from aromatics.

As illustrative of the application of my new catalyst to isomerizing,the following example of isomerizing natural gasoline is given.

The process was carried out in a pressure reactor. The hydrogen fluoridewas first charged, followed by the natural gasoline and butylene. Borontrifluoride was then admitted under pressure. The reaction continued forone-half hour after which the mixture was stratified and the upperhydrocarbon layer withdrawn under pressure. A fresh gasoline charge wasthen introduced under pressure and treated with the catalyst remainingin the reactor. This was repeated, and the ninth to twelfth batches werepooled for analysis, as these were regarded as indicative of what mightbe expected from a truly continuous process.

Further data are as follows:

T Charge Stock 65353} HF (volume based on hydrocarbon) 78 BFa (partialpressure 25 Olefin (butylenc) (on hydrocarbon 2. 5 Temperature 90 TotalPressure 55 Time of Reaction "hours" The same procedure was repeatedexcept that no olefin was used in order to determine the effect of thenew catalyst as compared with hydrogen fluoride and boron trifluoridealone.

The results are as follows:

From the above analysis it will be seen that in accordance with theinvention the amount of iso-butane is desirably large, the amount ofpentane is reduced and the amount of iso-pentane increased. The knockrating of the heavier fraction is noticeably improved.

As illustrative of the application of the invention to the isomerizationof butane, a procedure was followed similar to that described above andthe samples from the ninth and twelfth isomerizations were analyzed.Further data are as follows:

Charge Stock Butunes HF (volume based on hydrocarbon) "percent" BFa(partial pressure) p. s. i.. 200 Olefin (butene) perccx1t. 2.2Temperature". .F 122 Total Pressure ...p. s. i.. 350 Time ..hours Theresults are as follows:

1 9th Isomeri- 12th isomerization zation Less than 04 0. 49 0.76Isobutane 15 51. 5 53. 2 Products heavier than Butane 6.49 9.13 PercentIsobutane based on n-butanc charge 15 40. 3 40. 8

Similar processes not using an olefin but using lower and higher partialpressures of boron trifluoride results in conversions of only 20.5% or27.2% respectively to iso-butane based on the butane charged.

In the first example it will be seen that the relatively mild conditionsare obtained by the low partial pressure of boron trifluoride. In thesecond example, where there is nothing higher than butane in the stockand where there need be less concern to avoid cracking, somewhatstronger conditions may be used, i. e. higher temperature and higherpartial pressure of boron trifluoride.

As illustrative of the application of the invention to cracking, thefollowing example is given of cracking natural gasoline (containingmostly pentane and hexanes) The procedure followed is that describedpreviously except that only two samples were treated, the second usingthe catalyst remaining after the first treatment.

Further data and results are as follows:

First Second treatment treatment Natural gasoline 90 98 Butylene 10 2 HF(based on charge) vol. per cent 25 0) Temperature F 130 Time hours.. BF;partial pressure p. s. i 150 Total pressure p. s. i 207 207 1 Lowercatalyst layer from first treatment.

The products formed are as follows:

Charge First Second treatment treatment Less than Butane O. 0 1. 48 0.12 Iso-butane. 0. 6 23. 5 6. 75 N-butane l0. 3 7. 5 10. 15 Isopentane-20. 6 28. ii 17. 30 Pentane 22.0 1. 3 2i. 7 Above pentane. 45. 5 22. 041. 03 Lower layer 19. 7 19. 7

In the above it will be noted that most of the product formed isiso-butane because such a light stock is selected for cracking.

A comparison of the products formed in this example with the firstexample from the same 9 stock will show the effect of more drasticconditions in this example, i. e., higher temperature and partialpressure of boron trifluoride change the process from one ofisomerization to cracking.

The process may be applied similar to the cracking of heavier stockunder about the same conditions.

When the process is applied to averaging, nbutane and kerosene may bereacted under conditions about intermediate between those given abovefor isomerizing and cracking. The olefin may be admitted to the mixerthrough a separate valve or may be in admixture with the butane that isused in the averaging process.

In another application of the catalyst, propane and pentane may beaveraged to form butanes in which process there is a net consumption ofthe propane and the pentane. In such a process the temperature may beabout 175 to 190 F., a partial pressure of boron trifluoride of 150pounds per square inch and a total pressure of 500 to 700 pounds persquare inch (because of the low boiling point of the propane). An olefinsuch as propylene is contained in the propane feed.

My invention is capable of many applications and embodiments as will beapparent to one skilled in the art in view of the disclosure herein, andall are to be included as are within the scope of my claims.

I claim:

1. A method of preparing a catalyst for use in efiecting isomerizationof normal paraffins under isomerizing conditions, which comprisesbringing together liquid hydrogen fluoride, and boron trifluoride undera partial pressure of -550 pounds per square inch, in contact with anormal paraflin to be isomerized and to 25 weight percent of an olefinbased on the weight of the hydrocarbon to be isomerized, said amount ofolefin being merely that which modifies the catalytic activity of thefluorides in effecting the isomerization of the normal parafiin as theprimary reaction.

2. A method of preparing a catalyst for use in effecting isomerizationof normal butane under isomerizing conditions, which comprises bringingtogether liquid hydrogen fluoride, and boron tri- Number Name Date1,187,775 Oswalt et a1 June 20, 1916 2,217,019 Ipatielf et a1. Oct. 8,1940 2,240,134 Egloff Apr. 29, 1941 2,276,171 Ewell Mar. 10, 19422,285,785 Seguy June 9, 1942 2,315,078 Pines et a1. Mar. 30, 19432,340,934 Connolly Feb. 8, 1944 2,347,274 McAfee et a1 Apr. 25, 19442,411,992 Krosse et a1. Dec. 3, 1946 FOREIGN PATENTS Number Country Date313,067 Great Britain Acc. June 5, 1929 fluoride under a partialpressure of 5-550 pounds per square inch, in contact with the normalbutane to be isomerized and /2 to 2 /2 Weight percent of an olefin basedon the normal butane to be isomerized, said amount of the olefin beingmerely that which modifies the catalytic activity of the fluorides inefiecting the isomerization of the normal butane as the primaryreaction.

3. A method of preparing a catalyst for use in effecting isomerizationof normal butane under isomerizing conditions, which comprises bringingtogether liquid hydrogen fluoride and boron trifluoride under a partialpressure of 5-550 pounds per square inch in contact with the normalbutane to be isomerized and 2 /2 Weight percent of butene based on thenormal butane to be isomerized, said amount of butene being merely thatwhich modifies the catalytic activity of the fluorides in effecting theisomerization of the normal butane as the primary reaction.

ROBERT E. BURK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Ipatieff Catalytic Reactions atHigh Pressures and Temperatures, Macmillan, N. Y., 1936, pages

